The invention relates to a process reactor for the electro-dynamic fragmentation of particulate mineral materials immersed in a processing fluid by pulsed high-voltage discharges and a method for operating the process reactor.
In its basic design, such a process reactor comprises: A closed reaction chamber with a funnel-like bottom including a central outlet. An electrode to which a high voltage can be applied, that is a high voltage electrode, extends from the top into the reaction chamber. This electrode is surrounded by an electrical insulation except for a free end area thereof. The high voltage electrode is movable along the axis thereof so that its end is disposed opposite the central outlet at the funnel-like bottom of the reaction chamber which outlet has a circumferential metallic edge that forms the opposite electrode which is at an electrical reference potential. Material is supplied to the reaction chamber for fractioning continuously or batch-wise by way of an opening in the wall of the reaction chamber.
The majority of the known fragmentation devices are operated batch-wise, or, in the language as used by the persons skilled in the art, in a batch-mode, that is, a small amount in the order of several kilograms of the material to be treated is introduced into the process space usually by hand and deposited above the reference electrode, generally on a perforated bottom wall (sieve) and is fragmented there by high voltage discharges. When the desired number of discharges has been reached, the materials that have passed through the sieve and the material remaining on the sieve can be discharged separately. A typical representative of the mode of operation is the Franka-O-plant of DE 195 34 232 C2 (FIGS. 5, 6) or, respectively, similar plants as they are described for example in publication [1].
For industrially relevant throughputs a batch-mode however is not particularly suitable. The apparatus disclosed in [2] is for a continuous supply of material but, because of the sieve used, it is not suitable for relatively large mass-throughputs.
U.S. Pat. No. 6,039,274 (FIG. 1) also discloses a continuous material flow in connection with a sieve or, respectively, a vibration sieve; however, there are unsolved points, that is, the throughput, the treatment duration and the life of the sieve.
The continuously operating processes patented in DE 197 27 534 C2 and GB 1 284 426 are based on the use of the electro-hydraulic principle, that is, the effects of the shock waves resulting from an underwater HV-discharge. Generally, it can be said that an important weak point of all apparatus concerns the sieve bottom in the process chamber which allows only a relatively small throughput volume and the largest added component which is allowed to leave the process area is always smaller than the mesh width of the sieve. In praxis, the conditions are even less favorable: If a component part is freed from the material and if that part is not disposed above an opening in the sieve bottom but reaches that location only after several more discharges it can be subjected to one or more additional fragmentation actions. This effect however is not desirable if, in addition to the basic requirement for fragmentation, the components should maintain a certain size which, in a heterogeneous material, may play an important role. As an example, the segregation of concrete into its constituents is referred to where the operation over a sieve electrode will inevitably result in an undesirable shift of the gram size distribution curve (grading curve) of the regained aggregate (gravel) towards smaller particle size. A direct mixing of new concrete on the basis of this recycled aggregate is therefore not possible. If such a grading curve shift or the undesirable fractioning procedure is to be avoided, a sieve with a larger number of openings and larger diameter openings must be used. However, with sieves having a larger number of openings, the probability of sieve failure or fractures increases and, with sieves having larger openings not only the material components of the desired size, but also smaller components with residual attachments of the cement matrix and matrix conglomerates pass through the openings. This again is contrary to the requirement for a separation of the components which is to be as complete as possible.
Sieves, furthermore, have the important disadvantage that they all have a tendency to clog as a result of foreign materials in the concrete waste, such as nails or reinforcement residues which detrimentally affect the operability of a technical plant.
It is therefore the principal object of the present invention to provide a process reactor for a preferably continuous and efficient electro-dynamic fragmentation of brittle particulate mineral materials for industrial relevant mass throughputs.